Breast hypoplasia denotes under-development of glandular parenchyma beyond two standard deviations from age-specific norms. The condition may be unilateral or bilateral, isolated or associated with systemic syndromes. Recognition is based on quantitative and qualitative deviations from expected breast morphology rather than on isolated patient perception.

1. Deficient breast volume
   A mammary projection that remains ≤ Tanner stage II after age 16 years, or a breast circumference difference ≥ 150 mL compared with the contralateral side, defines objective hypoplasia.
2. Asymmetry
   Unilateral hypoplasia produces visible volume discrepancy, often accompanied by contralateral hypertrophy; the nipple-areolar complex is smaller and may lie more superiorly on the affected side.
3. Tuberous configuration
   A narrow base with a constricted inframammary fold, enlarged areola, and herniation of glandular tissue through the areolar opening creates a “tube-like” shape; this variant is frequently bilateral.
4. Absence of the inframammary fold
   A flat chest wall contour without the normal curved sub-mammary crease indicates insufficient lower-pole expansion and is typical of severe hypoplasia.
5. Hypoplastic or absent nipple-areolar complex
   The areola may be < 2 cm in diameter, pale, or lightly pigmented; true anonychia (absent nipple) is rare and suggests ectodermal dysplasia or Poland sequence.
6. Associated chest-wall deformities
   Pectus excavatum, carinatum, or rib abnormalities often coexist; rib hypoplasia and absence of the pectoralis major muscle point to Poland syndrome.
7. Endocrine stigmata
   Delayed menarche, primary amenorrhoea, or sparse axillary/pubic hair suggests underlying hypogonadotropic hypogonadism; galactorrhoea may indicate hyperprolactinaemia.
8. Psychosocial impact
   Significant distress, avoidance of tight clothing, and asymmetry-related postural changes are common; body-dysmorphic concerns may persist even after reconstructive surgery.